A common element used in optical systems is known as a beam splitter. Beam splitting optical assemblies and elements play an integral role in optical systems by splitting, combining, and controlling the directions of multiple beam paths. Specialized thin film coatings applied to optical surfaces divide beams of light into separate wavelengths and polarization states with specific targeted values of transmittance and reflectance.

Beam splitters are used in a variety of optical applications, from commercial SLR cameras, to LCD projectors, to modern FLIR systems. They are also heavily relied upon within laser systems. For example, a beam splitter is an essential element of an interferometer where the beam splitting aspect of the component literally generates the interference of the instrument.